Natural gas hydrates (NGH) are prone to causing pipeline blockage in flow assurance, attracting considerable attention in the petroleum industry. This work reviews the significant progress in hydrate flow assurance research in China. Gas hydrate structures are briefly introduced to provide a basic understanding, while the application and development of hydrate management strategies in China are summarized. Subsequently, the development and improvement of hydrate phase equilibrium models are presented, which have been widely applied to the practical challenges of flow assurance. Moreover, kinetics research involving hydrate nucleation, growth, and decomposition are summarized, including nucleation mechanisms, induction time, memory effect, hydrate growth at different interfaces, hydrate growth at a microscopic level, and hydrate decomposition under different systems. The current research status of hydrate slurry flow is also analyzed in detail, covering the viscosity and flow resistance of hydrate slurry and the mechanisms of hydrate particle aggregation, deposition, and blockage. In addition, even though the numerical models of hydrate slurry multiphase flow have been sorted out, the accurate quantitative calculations and risk assessments are still in the initial stage, presenting significant room for improvement. Although substantial research progress has been made in China regarding gas hydrate flow assurance, considerable effort should be devoted to further understanding the intrinsic mechanism work to improve the applicability of various models. This review discusses the current developments, existing problems, and future prospects in the various basic hydrate flow assurance fields in China. It aims to provide readers with an overview of hydrate flow assurance research in China, hoping to provide a reference for developing this field.

No abstract

The Kuro-dake Campsite in Daisetsuzan National Park is situated in a fragile alpine setting. Since it opened in 1992, it has not been under formal management. With camping increasingly affecting the Kuro-dake Campsite, this study aims to gain deeper insights into the soil erosion and overcrowding at the campsite and to suggest a corresponding strategy for future management. A detailed topographic map was created using pole photogrammetry to understand the ground surface condition of the campsite in 2017. Aerial photographs taken in 2012 and 2017 were used to understand the long-term changes in the ground surface. Furthermore, questionnaire surveys with campers, interview surveys with organizations related to the park management and secondary data collection were conducted. Two gullies were identified on the topographic map of the campsite. From 2012 to 2017, the campsite size increased by 48 m2. The daily-use level on busy days is nearly seven times the mean daily-use level for the year. Some campers illegally pitch tents on nearby trails on such busy days. The questionnaire surveys in 2017 and 2018 (n = 346) show that most respondents oppose a future closure of the campsite and two-thirds oppose a use limit. The 2018 survey (n = 210) shows that 71% of respondents were not aware of the reservation system in national parks elsewhere; however, 76% agreed to a reservation system to secure their tent space. Introducing formal management oversight, along with a reservation system, is urgently needed.

No abstract

No abstract